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-rw-r--r--arch/x86/kernel/tsc.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 599e581..9e80207 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -315,6 +315,15 @@ static unsigned long quick_pit_calibrate(void)
outb(0xff, 0x42);
outb(0xff, 0x42);
+ /*
+ * The PIT starts counting at the next edge, so we
+ * need to delay for a microsecond. The easiest way
+ * to do that is to just read back the 16-bit counter
+ * once from the PIT.
+ */
+ inb(0x42);
+ inb(0x42);
+
if (pit_expect_msb(0xff)) {
int i;
u64 t1, t2, delta;
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